In forming dielectric articles such as semiconductor integrated circuit devices it is desirable to utilize capacitive elements that have high capacitance in small dimensioned, planar structures to improve the electrical performance and particularly to improve the response of integrated memory circuits. A typical capacitor comprises a pair of electrode layers having dielectric material therebetween. Voltage is applied across the electrode layers and a charge is stored in the capacitor with the amount of charge being storable in the capacitor, e.g. the capacitance, being proportional to the opposing areas of the electrodes and the dielectric constant of the dielectric material. Capacitance has been also found to be inversely proportional to the thickness of the dielectric material, thus thin film capacitors are generally seen as a preferable means to achieve high performance. Problems still exist however, in optimizing the performance of thin film capacitors, so there is a continuing need to improve electrical properties, such as attaining higher dielectric constants, lowering charge dissipation factors and lowering leakage currents.
European Patent 46,868 discloses fabrication of capacitor structures using dielectrics having high dielectric constants and discusses some of the problems associated therewith, particularly the tendency of dielectric materials having a high dielectric constant to degrade rapidly at higher temperatures and their attendant leakage. The European patent proposes to resolve such problem by forming a capacitor structure that includes dual dielectric layers, comprising a first dielectric layer of silicon nitride or aluminum oxide and a second layer selected from a specific group of selected metal oxides and titanates. Such dual layered dielectric capacitors are said to have high capacitance (.epsilon./t&gt;0.04) and satisfactory E.sub.b and dielectric loss.
U.S. Pat. No. 4,734,340 discloses an improved thin film capacitor wherein a particularly thin film dielectric layer, having high dielectric capacitance, is deposited by a sputtering technique and comprises a mixture of tantalum and titanium oxides.
U.S. Pat. No. 4,803,591 discloses an improved capacitor comprising layers of dielectric ceramic compositions of high dielectric constant. The ceramic compositions are characterized as comprising magnesium dioxide together with barium titanate, niobium pentoxide and zinc oxide. The capacitor formed from such ceramic compositions are said to have a high dielectric constant with decreased temperature dependency over a wide temperature range.
U.S. Pat. No. 4,873,610 discloses a dielectric article having a laminate of plural thin film dielectric material layers, comprising a combination of dielectric material layers, that have different temperature characteristics of permittivity. The patent specifies that opposing laminates constitute different dielectric compositions for attaining adjacent layers having different temperature characteristics of permittivity. The reference does not disclosure or infer that layers constituting the same dielectric material can have different temperature characteristics of permittivity.
U.S. Pat. No. 4,931,897 discloses a semiconductor element and method of manufacture wherein a lower electrode, having a polycrystalline silicon film thereon, is treated so that the silicon film comprises an amorphous silicon surface. A thin film of dielectric material is thereafter deposited on the amorphous silicon surface in such manner that the amorphous surface does not recrystallize to a polycrystalline form. The stated objective of the patent is to produce an interface, between the polycrystalline silicon film serving as the lower electrode and the dielectric film, that is flat and uniform to prevent pinholes and electric field concentration. The reference does not disclose the formation of a dielectric film having an amorphous and a polycrystalline layer.
Thus, though the prior art is replete with proposed solutions for manufacture of optimized dielectric articles, such solutions have not sufficiently met the ever increasing demands of the emerging industry for their various uses.
An object of the instant invention is to provide dielectric articles which reduce the leakage problems associated with the use of the various dielectric films.
Another object of the invention is to provide a thin film capacitor that has improved resistance to leakage and has resistance to electric field concentration.
A further object is to provide a method for the formation of thin film dielectric articles that reduces leakage and/or electric field concentration.
A still further object is to provide a thin film capacitor that has improved capacitance per unit film area.
These and other objects of the invention will be apparent from the following recitation.